(a) Technical Field
The present invention relates to a method for preparation of a transition metal electroplated porous carbon nanofiber composite for hydrogen storage with increased hydrogen storage capacity comprising electroplating a transition metal with controlled particle diameter and surface dispersion on porous carbon nanofiber having predetermine specific surface area, pore volume and diameter.
(b) Background Art
With the development of industries, the consumption of fossil fuels including oil, coal, natural gas, etc. accounts for 90% or more of the total energy consumption. However, fossil fuels cannot be recycled after use, and are expected to be depleted in 50 to 100 years. Besides, various pollutants generated during the burning of the fossil fuels have been threatening the mankind with severe environmental problems such as global warming, destruction of the ozone layer and acid rain. Accordingly, the development of alternative energy sources, which are clean and safe and are not depleted, is required. Fundamentally, there is an urgent need for a new energy system not relying on fossil fuels.
In this regard, natural energy sources such as solar heat, subterranean heat, wind force, ocean energy, etc., and hydrogen energy using water are viewed as promising alternative energy sources. A fuel cell system using hydrogen is without the problem of depletion, because hydrogen can be produced unlimitedly from water. Further, there is no generation of environmental pollutants, e.g., carbon dioxide (CO2), at all. Such a fuel cell system requires a hydrogen storage medium. Recently, researches have been actively carried out focusing on carbon materials for use as a hydrogen storage medium.
Although consisting of single elements, carbon materials are superior in chemical stability, electrical and thermal conductivity, strength, elasticity, biological affinity, etc., because of various bonding types. Further, they are advantageous over conventional hydrogen storage media such as high-pressure hydrogen storage media, liquefied hydrogen, silica, metal-organic frameworks (MOFs) and metal hydrides, because they are safer, lighter, less expensive, more stable and environment-friendly because they can be recycled. In addition, through a series of activation processes, the carbon materials can be transformed into ultra-porous materials with exceptionally high specific surface area incomparable with other materials. Such porous structures have been utilized for adsorption of hydrogen or other gases. Through adequate control of the pore structure and the surface characteristics, the carbon materials can be transformed into highly functional hydrogen storage media.
Until now, the hydrogen storage mechanism of carbon nanotube has not been elucidated clearly. And, the carbon nanotube is disadvantageous in that it has limited hydrogen storage capacity at room temperature. Ye et al. [Appl. Phys. Lett. 74 (1999) 2307] have reported that up to 8 weight % of hydrogen storage was attained using a single-walled carbon nanotube. But, this was a result obtained under ultra-low temperature (80 K) and high pressure (40 bar). At present, no case is reported in which a hydrogen storage capacity of 1 weight % or better has been attained at room temperature and normal pressure.
Hydrogen storage using carbon materials is advantageous over high-pressure hydrogen storage or liquefied hydrogen storage, in safety and cost. Further, it is semi-permeable because the associated reaction is reversible. However, the porous carbon itself has insufficient affinity for hydrogen molecules, and the hydrogen storage capacity at room temperature is not so great because of low adsorption energy. According, there have been attempts to greatly improve hydrogen storage capacity by modifying the existing carbon materials. However, in the conventional methods, only metal salts have been added to various carbon materials.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.